Sheet metal is used in nearly all products, and range from the simple such as the tab on a pen, to the complex such as the skin on an aircraft. In general the sheet metal is press formed or stretch formed into the required shape. Press forming is generally accomplished by pressing the sheet metal between form dies that bend or impart the proper contour into the sheet metal. Stretch forming is generally accomplished by stretching the sheet metal over the form die to impart the proper contour into the sheet metal.
The contour of the form die is generally different from the contour imparted into the sheet metal due to the spring back of the sheet metal during the forming process. The contours of the form die are generally varied until the correct contour is imparted into the sheet metal.
One type of conventional form die is a machined form die. The machined form die is produced by machining the contours into the die to impart the correct contours into the sheet metal. Conventional machined form dies have several disadvantages. For example, machined form dies cannot be easily reworked and often have contour and surface finish requirements that are expensive to produce. In addition, machined form dies are generally large and bulky, making them expensive to store and maintain.
Another type of conventional form die is a self-adjusting discrete element form die. The self-adjusting discrete element form die generally has pins that can be adjusted to vary the height of each pin relative to the other pins. The variation in height of the pins forms the contour in the form die that is imparted into the metal product. The pins are mechanically adjusted to the required height. Some self-adjusting discrete element form dies require manual adjustment of the pins, whereas, other self-adjusting discrete element form dies use a computer controlled automated adjustment system. Conventional self-adjusting discrete element form dies have several disadvantages. For example, self-adjusting form dies are often prohibitively expensive. In addition, self-adjusting form dies can be damaged by the application of high compressive loads that are required in some die forming processes.